The objectives of the proposed project are to visualize, identify, and characterize morphologically several of the major transmembrane macromolecules associated with synaptic transmission and electrogenesis at the mammalian neuromuscular junction. Initially, ultrastructural identification of the morphological correlate for the acetylcholine (ACh) receptor will be accomplished using a combined immunological labelling - freeze-fracture - serial thin sectioning technique developed in this laboratory and previously employed for the ultrastructural identification of ACh receptors in an in vitro system. Similar labelling techniques will be applied toward the positive identification of two other membrane integral proteins - the sarcolemmal "square array" and the electrically sensitive sodium channel. The techniques developed and data obtained during the proposed research program will 1) permit identification and quantitation of a number of macromolecules associated with chemical excitability and electrogenesis in mammalian nerves and muscles, 2) have immediate practical application in the analysis of the molecular alterations in the etiology of specific neuromuscular diseases (e.g., Myasthenia Gravis) and 3) contribute to a better general understanding of the structure and function of biological membranes at the molecular level.